package org.apache.maven;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;

import org.apache.maven.execution.ProjectDependencyGraph;
import org.apache.maven.project.MavenProject;
import org.apache.maven.project.ProjectSorter;

/**
 * Describes the inter-dependencies between projects in the reactor.
 * 
 * @author Benjamin Bentmann
 */
class DefaultProjectDependencyGraph implements ProjectDependencyGraph {

  private ProjectSorter sorter;

  /**
   * Creates a new project dependency graph based on the specified project sorting.
   * 
   * @param sorter The project sorter backing the graph, must not be {@code null}.
   */
  public DefaultProjectDependencyGraph(ProjectSorter sorter) {
    if (sorter == null) {
      throw new IllegalArgumentException("project sorter missing");
    }

    this.sorter = sorter;
  }

  public List<MavenProject> getSortedProjects() {
    return new ArrayList<MavenProject>(sorter.getSortedProjects());
  }

  public List<MavenProject> getDownstreamProjects(MavenProject project, boolean transitive) {
    if (project == null) {
      throw new IllegalArgumentException("project missing");
    }

    Collection<String> projectIds = new HashSet<String>();

    getDownstreamProjects(ProjectSorter.getId(project), projectIds, transitive);

    return getProjects(projectIds);
  }

  private void getDownstreamProjects(String projectId, Collection<String> projectIds, boolean transitive) {
    for (String id : sorter.getDependents(projectId)) {
      if (projectIds.add(id)) {
        if (transitive) {
          getDownstreamProjects(id, projectIds, transitive);
        }
      }
    }
  }

  public List<MavenProject> getUpstreamProjects(MavenProject project, boolean transitive) {
    if (project == null) {
      throw new IllegalArgumentException("project missing");
    }

    Collection<String> projectIds = new HashSet<String>();

    getUpstreamProjects(ProjectSorter.getId(project), projectIds, transitive);

    return getProjects(projectIds);
  }

  private void getUpstreamProjects(String projectId, Collection<String> projectIds, boolean transitive) {
    for (String id : sorter.getDependencies(projectId)) {
      if (projectIds.add(id) && transitive) {
        getUpstreamProjects(id, projectIds, transitive);
      }
    }
  }

  private List<MavenProject> getProjects(Collection<String> projectIds) {
    List<MavenProject> projects = new ArrayList<MavenProject>();

    for (MavenProject p : sorter.getSortedProjects()) {
      if (projectIds.contains(ProjectSorter.getId(p))) {
        projects.add(p);
      }
    }

    return projects;
  }

  @Override
  public String toString() {
    return sorter.getSortedProjects().toString();
  }

}
